Recording/playback systems for magnetic medium are subject to degradation during use as a result of the accumulation of debris which occurs on the magnetic transducer head(s) of such systems. Transducer heads include magnetic read/write heads and associated read/write elements. Hence, a need exists to periodically clean magnetic transducer head(s). Accordingly, several different techniques have been developed for cleaning a magnetic transducer head as discussed below. However, each technique still has shortcomings that require further improvements.
One prior art technique utilizes a separate, dedicated "cleaning cartridge" to perform periodic cleaning of the recording transducer. A "cleaning cartridge" contains a supply of unrecorded abrasive tape that is used to clean one or more magnetic transducer heads. For example, the recording heads found on a tape drive can be cleaned with a "cleaning cartridge". In order to utilize a "cleaning cartridge", the recording/playback of the medium must be stopped, with the data cartridge being removed, and the cleaning cartridge being inserted. The "cleaning cartridge" is then run within the record/playback system so as to clean the recording transducer. Once cleaning is complete, the "cleaning cartridge" is removed, and a data cartridge is reinserted. However, after the "cleaning cartridge" has been used, a new data cartridge may be loaded into the system in order to evaluate the performance of the magnetic transducer head so as to confirm that cleaning has been successfully completed.
Where the magnetic recording/playback system is a tape recording/playback system, the cleaning cartridge includes an abrasive cleaning tape that can cause excessive tape head wear. The abrasiveness of the cleaning tape can be adjusted in order to tailor its effectiveness. If the cleaning tape is made sufficiently effective to thoroughly remove debris from the read/write heads, then the cleaning tape should only be used when it is necessary; otherwise, excessive head wear will result. Such a problem can occur where a piece of abrasive cleaning tape is provided as a leader on a data tape cartridge such that each time a tape is used the leader is used to clean a read/write head. Furthermore, the provision of an abrasive tape leader within a data tape cartridge eventually results in degradation of the abrasive leader from debris accumulating on the cleaning tape. If the abrasive cleaning tape is made sufficiently effective to thoroughly remove debris from a magnetic head, then a routine must be established to limit use of the cleaning tape only when it is necessary. However, sufficient cleaning may not be realized.
Where magnetic tape is used to store computer data, the presence of errors represents a significant problem even if the errors occur infrequently. In certain applications, the loss of data requires that a user be able to perform a cleaning operation in response to recognized drop-out errors, but does not immediately prevent use of the equipment prior to cleaning. In some cases, the loss of a single bit of computer data can be of significant importance, and recovery from such an error must be done in a manner that ensures error-free data storage and retrieval. While error correction is possible via error correction algorithms, data loss can still present problems to a user.
One form of magnetic storage comprises existing linear and helical scan tape drives that are used for storage and retrieval of computer data. Such tape drives can use a single reel in the form of a magnetic tape cartridge to house the magnetic tape media. A special leader or leader block is attached to the magnetic tape media at one end which enables the tape drive to extract the magnetic tape from the magnetic tape cartridge.
"Tape recorder" is intended to refer to one form of magnetic recording/playback system comprising magnetic tape transcription equipment. Such equipment is understood to include standard tape recorders having fixed or movable heads, as well as arcuate scan and helical scan transcription equipment as is typically used in analog and digital tape recorders. According to one implementation, a linear transcription head is employed, although such invention has application in other tape recording environments. As described here, "transcription" is intended to mean read and/or write operations that are performed with a tape recorder, and is not intended to be limited to a particular use or format for data.
Another prior art technique is found on a typical helical scan tape drive wherein a head cleaning device is built into a mechanism of the tape drive. More particularly, a helical scan tape drive forms a recording method that is used on videotape and digital audio tape (DAT) that runs the tracks diagonally from top to bottom in order to increase the storage capacity. A drum containing read/write heads is used to read/write information in diagonal segments from/onto a segment of magnetic tape. A head cleaner is located on an opposite side of the drum than the tape. In this manner, while data is being written/read, the head cleaner can be concurrently cleaning the heads as they pass by on the drum.
In contrast, a linear tape drive continuously presents a magnetic tape segment in contact with the read/write heads, unless the tape is removed from the tape drive. Hence, linear tape drives typically do not have head cleaners built into the tape drive mechanism. Therefore, a data tape is typically removed when it is determined that the heads have become dirty in order that a cleaning tape cartridge can be loaded into the tape drive to clean debris from the heads. However, such loading/unloading is undesirable because it takes customer intervention and a significant amount of time to spool the tape back into the cartridge. Accordingly, such loading/unloading is slow, cumbersome and is extremely difficult to implement automatically.
One linear tape drive which does have a head cleaner built into the tape drive mechanism is the International Business Machines (IBM) Magstar 3590, sold by IBM Storage Systems Division, 9000 S. Rita Road, Tucson, Ariz. 85744. The IBM Magstar 3590 has a cleaning brush built into the tape drive mechanism such that the cleaning brush is brought into contact with the read/write heads during a tape threading operation. More particularly, as a leader block on a data tape is pulled back into the tape cartridge, the leader block hits a lever which engages the brush against the read/write heads. An actuator moves the heads up and down in order to provide scrubbing action between the brush and heads. However, such cleaning action only takes place after the data tape has been retracted into the data cartridge. Furthermore, it takes time to spool the tape back into the cartridge which causes delay, even before actual brush-to-head cleaning action actually occurs.
It is therefore desirable to employ an improved tape drive cleaning mechanism that is capable of sufficiently cleaning a magnetic head of the system without imparting any significant delay in operation resulting from unwinding a data tape back into a data cartridge before cleaning can begin.
It is further desirable to deliver such cleaning action without having to remove a data tape from a tape drive. Furthermore, there is a desire to deliver cleaning to a head at periodic intervals that substantially coincide with a need to clean debris from a magnetic head.